Method of plasticizing a resin and forming it into a sheet



July 7, 1936. E H` HAUX 2,046,378

METHOD OF PLASTICIZING A RESIN AND FORMING IT INTO A SHEET Filed Dec. 22, 1954 2 sheets-sheet 1 mm1- ranuv INVENTOR. EL MEE Hna )K BY @g AT ORNEYS.

22, 1934 2 sheets-sheet 2 E. H. HAUX July 7, 1936.

METHOD OF PLASTICIZING A RESIN AND FORMING IT\INTO A SHEET Filed Dec.

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Patented July 7, 1.936

METHOD OF 'PLASTICIZING A RESIN AND FORMING IT INTO A SHEET l Elmer H. Haux, Tarentum, Pa., assignor to Duplate Corporation, a. corporation of Delaware Application December 2z. 1934, serial No. '158,782

` s claims. (ci. 10e-22) The invention relates to a method for plasticizing a synthetic resin and forming it into a sheet which may be used as the interlayer in safety glass or for any other purpose for which the material may be adapted. The invention has for its principal objects the provision of an improved method for very thoroughly mixing a resin and its plasticizer at a low cost, and for getting it into sheet form suitable for use, the latter object being secondary, however, since the resin plasticized by the improved method may be cake pressed and sheeted or utilized for purposes other than the formation of sheets if desired. The invention is hereinafter. described in connection l5 with a vinyl resin, such as vinyl acetal, or vinyl chlor acetate, and the plasticizers and solvents are those particularly adapted for use with this particularresin, but it will be understood that the invention is of broad application and may be used zo with many other resins, such as the Glyptals, condensation products of the toluene sulfonamide group, and the like. In the plasticizing of such other resins, the plasticizers and solvents employed will be selected to meet the requirement of the particular resin, a wide range being available and well known to those skilled in the art.

As examples of the plasticizers which may be used with the vinyl resins either alone or in combination are the following: diethyl phthalate, dibutyl phthalate, tributyl phosphate and methyl cellosolve phthalate. l

In carrying out the process, the resin is incorporated into a mixture which includes one or more of the above plasticizers and also a quantity of resin solvent, such as methyl alcohol, butyl alcohol, isoproponol or monoethyl ether of ethylene glycol.I The use oi. this solvent insures a very thorough mixture of the resin and the plasticizer. It i`s now necessary to separate the solvent from the mixture, and this is accomplished by treating the mixture with some liquid which will mix with the solvent, but which is not a solvent of the resin and plasticizer. 'I'his requirement is met by the use of water, the treatment of the mixture with water causing the plasticized resin to form a precipitate. The precipitate mixed with water and solvent may be conducted away continuously in the form of a mat layer which is dried to remove any water and solvent .50 therein, thus giving a continuous sheet, or the precipitate may be extruded as a sheet, or formed into a more or less solid cake and dried preliminary to cutting into sheets. The precipitate may also be shaped into any other desired form 55 depending on the use to which the product is to be put. The drawings illustrate the practice of the invention in forming a continuous sheet.

Figure 1 is a diagrammatic side elevation of the i'lrst part of the apparatus. Fig. 2 is a similar view of the second part of the apparatus. And Fig. 3 is a section through a modiiication of a part of the apparatus of Fig. 2.

Referring to the drawings, I, 2, and 3 are containers respectively for water, solvent and plasticizer; 4 is a mixer for the solvent and plasti- 1o cizer; 5 is a container for the resin which is to be treated; 6 and 'I are additional mixers; 8 is a shallow feed tank or trough which receives the mixture from the tank 1; 9 is a screen conveyor over which the layer of material from the trough 15 'I is carried to form it into a sheet; I0 is another conveyor for conducting thesheet through a heated body of liquid II, during which passage the sheet is colloided due to the application of heat and the pressure applied by the rolls I2; 20

I3 and I4 are two series of calendering rolls for removing any liquid remaining in the colloided sheet; and I5 is a drum on which the nished. sheet is wound.

As the first step in the operation, quantities 25 of solvent and plasticizer from the tanks 2 and 3 are supplied to the mixer 4 which carries agi- I tating lmeans .driven from the motor IB, the solvent preferably employed being methyl alcohol and the plasticizer being diethyl phthalate. This 30 mixture together with water from the tank I is then supplied to form the mixture in the'tank 6 which has anagitator driven from the motor I1. The resin to be plasticized is now supplied from the container 5 through the pipe I8, such resin 35 being preferably vinyl acetal in solid form divided so that it will pass through a 20 to 40 mesh screen.

The resin is plasticized in the mixer. 6 and forms a precipitate therein, as heretofore explained, due to the fact that the solvent will go into 40 solution with the water which is not a solvent of either the plasticizer or the resin. The agitator, however, prevents the plasticized resin from settling so that it is maintained in suspension in the mixture, and is supplied through the connection 45 I9 to the mixer 1. The mixer is provided with an agitator driven from the motor 20. Additional water is supplied to this mixer through the supply pipe 2I having the control valve 22.

The mixture of water and solvent with the plasticized resin suspended therein is fed through the conduit 22a to the feed tank 8, a valve 23 serving to regulate the amount of ow. The tank 8 is pivoted at 23a at its forward end, and is supported at its rear end by means of a cable 24 65,

extending around the drum 275 of the hoist 2i. This drum is operated by means of the hand chain 21 which drives the drum through the reduction gearing 28. By this means the tank) may be tilted so as to regulate the flow of mixture or slurry to the screen conveyor 9. This screen conveyor passes around a pair of drums 29 and I0, one of which is suitably driven, and over a plurality of intermediate rollers 3l which are preferably hollow and provided with suction means to assistin withdrawing liquid from the mat layer passing thereover on the screen conveyor. A pair of spreading and leveling bars 32, l2 are preferably provided overthe forward end of the conveyor in order to level oif the mat layer. Water spray pipes 33 are also preferably employed over the conveyor, such pipes being fed from the supply pipe 33a. This additional supply of water serves to assist in washing out solvent which remains in the mat layer, an inclined floor 34 being provided beneath the conveyor for collecting the liquid which drains from the conveyor. This liquid is conducted away through the pipe 35 which leads to suitable means, not shown, for recovering the solvent. The mat layerl as it leaves the conveyor 9 passes beneath a presser roll 36 and into the body of liquid I I where it is car- .ries of presser rolls I2 which are arranged in opposition to the rolls 31 which lie'between the flights of the conveyor I0. The conveyor passes around suitably driven rolls at the ends thereof and the rolls I2 are also preferably'driven by means not shown. A hood I Ia is preferably'employed above the bath and has a conduit conducting away the moist gases.

The colloided sheet, as it emerges from the bath IIb for II, passes between a pair of presser rolls ll, 38

and over the rolls 39 to the series of calendering rolls I 3 and I4. These rolls are suitably heated, and the sheet is caused to pass back and forth around the two sets of rolls, so as to give the rolls an opportunity to heat the sheet and drive on any water and solvent remaining therein, thus curing the sheet and bringing it to a condition in which it may be used. vThe finished sheet is wound onto the drum I5 which is removed from time to time and replaced by other collecting drums.

Fig.3 illustrates a modification in which a different form of colloiding and heating means is substituted for the bath II of Fig. 2. In this substitute construction, an oven 40 is provided which encloses the pairs of driven presserrolls 4I between which the sheet is delivered from the presser rolls 42, 42 corresponding to the rolls Il) and 36 ofthe Fig. 2 construction. The oven 40 is lined with steam pipes 43 and 44 lying above and below the rolls 4I. Y Suitable supply pipes 45, 45 are provided for these pipes, and by this means, the oven may be heated to any desiredtemperature. The application of the heat, thus provided, in connection with the pressing effect of the rolls 4I, 4I serves to colloid the mat layer into a solid' sheet as in the construction of Fig. 2. The colloided sheet is delivered between a pair of presser calendering rolls as in the construction heretofore liquid which is forced from the sheet during the colloiding operation. f Y

- The proportions of resin, plasticiser.- solvent and water es used in the foregoing process may vary. For the purpose of illustration, the s amountswhichmaybemixedinthe tank I are as follows:

m Resin (vinyl acetal) 6' Ulasticizer (diethyl phthalate) 3.7 l0 Solvent (ethyl alcohol) -L.----- l2 Water 'I5 tated in the mixer 8 until the supernatant liquoris clear, indicating that the plasticizer has been absorbed by theresin. The mixture then is discharged into the tank I which contains 500parts of water, which is violently agitated to form a slurry and keep the plasticizer resin in suspension.

As heretofore explained, the process in its broader aspect may be practiced by precipitating gg the plasticized resin into a solid dough-like mass which may be formed. into -sheets by extruding through a slot or by cake pressing and sheeting. Proportions of resins, plasticizer and solvent which may be satisfactorily used in this method are as follows:

' Parts Resin (vinyl aceta1 12 Solvent (methyl alcohol) 88 Plasticizer (diethyl phthalate) 8 The above ingredients are mixed to form s clear solution of medium viscosity. This solution is poured into a large excess of water, i. e. about 1000 parts, which is being agitated. A thick dough-like mass is precipitated consisting of the plasticized resin and small quantities of water and solvent. This mass :ls not sticky and lends itself readily to extrusion through a slot or orifice to form sheets. It can also be dried and cake pressed and then. sheeted bythe known methods.

Other proportions of ingredients which may be employed in a similar process are as follows:

. Parts 50 Resin (vinyl acetal) 5 Solvent (isoproponol) -..'40 Plasticizer (tributyl phosphate) 40 Waterv l5 65 vwhich will form a solution with the solvent but which is a non-solvent of the resin and plasticizer, adding a ilnely divided resin to the mixture and agitating until the plasticizer has been absorbed by the resin, conducting the mixture into another body of said liquid and/agitating so that the plasticized resin is maintained in suspension,`conducting a layer of the mixture away from the bath continuously in the form of a mat 75 andere and dryins it to remove the solvent and liquid to provide a sheet of plastlcized resin.

2. A process of forming a sheet of plasticized synthetic resin which consists in mixing a plasticizer and solvent for the resin with a liquid which will form a solution with the solvent but which is a. non-solvent ot the resin and plasticizer, adding a finely divided resin to the mixture and agitating until the plasticizer has been absorbed hy the resin, conducting the mixture into another body of said liquid and agitatins so that .the plasticized resin is maintained in suspension, conducting a layer of the mixture away from the bath continuously in the form of amat and applying heat and pressure to the mat layer to colloid the plasticized resin..

3. A process of forming a sheet of plasticised synthetic resin which consists in mixing a plasticizer and solvent for the resin with a liquid which will form. a solution with the solvent but which is a non-solvent of the resin and plasticizer, adding s. nnely divided resin to the mixture and agitstins until the piasticizer has been absorbed by the resin, conducting` the mixture into another body of said liquid and agitating so that the plasticized resin is maintained in suspension,

conducting a layer of the mixture away from the bath continuously in the form of a mat and applying heat and pressure to the mat layer to colloid the plastieizeclv resin, and treating the sheet thus formed to remove the liquid and solvent remaining therein.

ELMERH.HAUX. 

